1. Field of the Invention
The present invention relates to an organic light emitting display, and more particularly, to a data driver and an organic light emitting display using demultiplexers, and the data driver supplies data signals for the same color to each demultiplexer.
2. Description of the Related Technology
Alternative to cathode ray tube (CRT) displays, flat panel displays are today popular. In particular, an organic light emitting display has excellent brightness and viewing angle characteristics, and thus, is believed by many to be the next generation of flat panel displays.
Unlike a liquid crystal display (LCD), the organic light emitting display employs a light emitting diode to emit light without a separate light source. Such a light emitting diode emits light corresponding to the a driving current flowing in an anode electrode.
FIG. 1 illustrates a conventional organic light emitting display.
The organic light emitting display includes a pixel portion 10, a scan driver 20, a data driver 30, and an emission control driver 40.
The scan driver 20 sequentially supplies scan signals to scan lines S1 through Sn in response to a scan control signal, i.e., a start pulse and a clock signal, from a timing controller (not shown).
The data driver 30 supplies data voltages corresponding to red (R), green (G) and blue (B) data to data lines D1 though Dm in response to a data control signal from the timing controller.
The emission control driver 40 includes a shift register, etc., and sequentially supplies emission control signals to emission control lines E1 through En in response to the start pulse and the clock signal from the timing controller.
The pixel portion 10 includes a plurality of pixels P11 through Pnm placed in regions where a plurality of scan lines S1 through Sn, a plurality of data lines DR1 through DBm, and a plurality of emission control lines E1 through En intersect with one another. Here, the pixel portion 10 displays an image corresponding to the applied data voltage.
Note that, one unit pixel Pnm includes red, green and blue sub-pixels PRnm, PGnm and PBnm.
The red, green and blue sub-pixels PRnm, PGnm and PBnm of the pixel portion 10 are structured to have the same pixel circuits, and emit red, green and blue light corresponding to the current applied to an organic light emitting diode, respectively. Thus, the pixel Pnm displays a color obtained by combining the light emitted by the red, green and blue sub-pixels PRnm, PGnm and PBnm.
The organic light emitting display is in need of m×3 data driving circuits supplying the data signals to m×3 (red, green and blue) data lines connecting the data driver 30 with the pixel portion 10. However, due to the size and the manufacturing cost of a panel, it is difficult to provide the organic light emitting display with a data driving circuit for each of the data lines. As the number of pixels increases, the organic light emitting display needs to have more data driving circuits.
FIG. 2 illustrates a data driver of the conventional organic light emitting display.
Referring to FIG. 2, the conventional organic light emitting display includes the data driver 30 having a demultiplexer 32.
The data driver 30 includes m demultiplexers 32 supplying the data signals to the data lines DRm, DGm, DBm corresponding to the red, green and blue sub-pixels PRnm, PGnm and PBnm of the pixel portion 10, respectively, and m data driving circuits 31 connected to the respective demultiplexers 32 and supplying the red, green and blue data signals to the respective demultiplexers 32.
Each data driving circuit 31 receives red, green and blue data from the timing controller and processes them in order to supply the red, green and blue data signals to data output lines DLm.
The data output lines DLm sequentially supply the red, green and blue data signals to input terminals of the demultiplexer 32.
The demultiplexer 32 sequentially supplies the data signals to the red, green or blue sub-pixels PRnm, PGnm and PBnm in response to the control signal of the timing controller, respectively.
Thus, one demultiplexer 32 supplies the data signals to three data lines DRm, DGmm and DBm, so that the number of data driving circuits is reduced to ⅓ of the number of sub-pixel columns.
However, in the conventional organic light emitting display, the organic light emitting diodes displaying red, green and blue of the pixel Pnm are different in emission efficiency according to colors, so that a gamma value should be selected for one data driving circuit 31 differently according to red, green and blue when all the red, green and blue data are processed by one data driving circuit 31. Therefore, even though white is displayed, the data driving circuit supplies red, green and blue data with different gamma values from thereby increasing power consumption due to the changes in data input.